1. Field of the Invention
The present invention relates to a method of splicing webs and, in particular, to a method of splicing webs such as flexible, strip-shaped metal plates, metal foils, flexible, strip-shaped films, and the like.
2. Description of the Related Art
This type of webs splicing step includes a method in which the ends of the webs are superposed on each other and then they are spliced together by means of a two-side adhesive tape or they are fused together by use of supersonic waves to be spliced together, a step of mechanically fitting the webs with each other, and a step of splicing the webs by welding.
In FIG. 3, there is shown an explanatory view of a conventional method of splicing webs by use of welding. As shown in FIG. 3, a following web 70 is unwound from a roll 72, is transferred to a pass roller 74 and then is delivered to a splicing apparatus 76. The splicing apparatus 76 includes a pre-cut device 78 which is in turn provided with cutters 80, 80. The leading end 70A of the following web 70 is cut by the pre-cut device 78 so that it can be butted accurately against the trailing end 82A of a leading web 82 to be spliced.
Downstream of the pre-cut device 78 there is arranged a welding device 84 which is composed of clamps 86, 88, and a welding torch 90. The leading end 70A of the following web 70 is to be held by the clamp 86 and the trailing end 82A of the leading web 82 is to be held, whereby the following web 70 and the leading web 82 can be butted against each other or slightly lapped on each other. As a welding method, a TIG arc welding method is employed in this case, but other welding methods are also available, including a MIG arc welding, a gas welding, a laser welding using CO.sub.2 or YAG, and the like. The welding torch 90 is situated above the butted portions of the webs, and is moved in the direction of the width of the respective webs 70, 82 to fuse the web ends 70A, 82A for welding. Also, if the thicknesses of the webs 70, 82 are respectively 0.3 mm or less, the webs 70, 82 to be spliced are fused very easily, and, therefore, in such case, it is preferred that the web ends 70A and 82A are lapped slightly on each other before they are welded.
Downstream of the welding device 84 there is arranged a rolling device 92 which includes a rolling roller 94 and a back bar 96. The welded portions of the following web 70 and leading web 82 can be rolled by means of operation of the rolling roller 94.
However, in the above-mentioned conventional web splicing methods, if one of the leading web 82 and following web 70 is twice or more in thickness than the other web, it is difficult to set up the splicing conditions when they are spliced by use of the supersonic waves or by welding. Also, if the materials and surface treatments of the webs are different from each other, it is difficult to splice such webs by means of the supersonic waves or by welding.
Since at present a process for carrying or delivering webs is complicated, the above-mentioned inconveniences cause the splicing portions of the webs, while the webs are being carried, to be folded repetitively, thereby producing complete folds in the web splicing portions, or cause the webs to be broken in the splicing portions because the web splicing portions are moved while they are given tension forces by the pass roller and the like. Also, at present there is an increased need for more varieties of products, and thus the shapes and materials of the webs must be diversified. However, the conventional splicing methods are not be able to cope with the production plans that include the above-mentioned increasing needs.
Referring now to FIG. 10, there is shown a perspective view of a lap splicing method according to the prior art. As shown in FIG. 10, metal webs 50 and 52 are lapped over each other, and the splicing portions 53 thereof are bonded by use of a two-side adhesive tape or welded together by use of supersonic waves (see FIGS. 4 and 6 of Japanese Patent Application Laid-open No. 59-24526).
However, with use of the prior art metal plate lap splicing method as shown in FIG. 10, the splicing portions 53 cannot be brought into contact with a pass roller and the like smoothly because the splicing portions are different in level from each other. Also, for example, in a step of coating a light-sensitive layer in manufacturing a plate for use in planography, when the splicing portions of the metal webs with a level difference pass through a coating device, the coating device must be retracted to prevent the metal webs from being damaged or broken. Further, if the coating device is not retracted, then the splicing portions 53 have ill effects on the coated conditions of the webs, resulting in the poor quality of the coated webs.
In addition to the above-mentioned drawbacks, in the prior art method, the whole surfaces of the splicing portions 53 cannot be adhered to each other very often, and, as a result of this, there is a possibility that the splicing portion surfaces 53 may peel off while the metal webs are in delivery. Additionally, in a method which includes a surface treatment step by use of a treatment solution, when the metal webs are caused to pass through the treatment solution, the treatment solution and the like may permeate into clearances in the splicing surfaces 53, which gives rise to the poor quality of the products in the following steps.
Also, in the above-mentioned prior art splicing methods, because it is necessary to position accurately the butting surfaces of the metal webs with respect to each other, it is difficult to butt the butting surfaces against each other quickly and accurately, requiring a lengthy operation. On the other hand, the operation to splice the metal webs is performed while they are being delivered and, therefore, in order to carry out the splicing operation without stopping the delivery line, an accumulator is used. However, the capacity of the accumulator is limited in that the time that can be allotted for the splicing operation also is limited. For these reasons, when the splicing operation, is extended with numerous metal webs having been delivered then the delivery line is forced to stop.
Referring further to FIG. 13, there is shown an observation view of the metal constitution of the sections of the welded, spliced portions of an aluminum plate having a thickness of 0.15 mm and an aluminum plate having a thickness of 0.3 mm which are lapped by 1.0 mm on each other and welded together by use of a TIG arc welding. As shown in FIG. 13, when the end portions 70A and 82A of the metal webs that are cold rolled are spliced, then in the spliced portions thereof there is produced a fusion portion 62, which first has been fused and then solidified, and in the peripheries of the fusion portion 62 there are produced recrystallized portions 64, 64, which have been heated by welding for a given period of time and thereby have been recrystallized. In other words, the welded spliced portions of the cold rolled metal webs include the fusion portion 62 that has been fused and solidified and the recrystallized portions 64, 64 that have been recrystallized under the influence of heat during welding. Additionally, in the peripheries of the welded spliced portions, there also are present mother material portions (which are the original metal webs) 66 in which none of the above-mentioned fusion, solidification, and recrystallization phenomena have occurred at all. That is, there are formed three metal structures in the spliced portions of the metal webs. Also, the welded spliced portions of the metal webs that have not been cold rolled can be classified into three metal structures, namely, a fusion portion, a recrystallized portion, and a mother material portion.
However, when the metal webs are welded and spliced according to the conventional welding and splicing methods, then the welded and spliced portions of the metal webs are sometimes different in thickness from the original metal webs. Also, when thin webs are lapped on each other by 2 mm or so, preferably 0.5 mm-1.5 mm and welded together to be spliced to each other, the thickness of the welded and spliced portions are greater than that of the original metal webs. If the thickness of the welded and spliced portions of the metal webs greatly differ from that of the original metal webs, when the metal webs having such welded and spliced portions are passed over a large number of pass rollers, then a stress concentration will occur in the welded and spliced portions, which may cause the welded and spliced portions to be broken. Especially when metal webs, which are different in thickness from each other, are spliced, then the stress concentration is extremely great.
Also, because of the mother material portion 66&gt;the recrystallized portion 64.gtoreq.fusion portion 62 in hardness and tensile strength, if a bending stress is given to a metal web having a structure in the order of the mother material portion, the recrystallized portion and the fusion portion, then the stress may be concentrated on the portion where the change of the thicknesses is great and, in this case, the recrystallized portion having a poor tensile strength is situated in such a portion. For this reason, if the metal webs having the spliced portions spliced according to the prior art splicing methods are passed over a large number of pass rollers, there is a possibility that they may be broken in a short time.